Search PubMed⌕ Search

Biomedical subjects

J Madar

Publications and source records attributed to J Madar.

At least 37 records · Page 2Linked to original sources
PubMed1987

Generation of lymphokine-activated killer cells does not require DNA synthesis.

We studied the role of DNA synthesis in the induction of lymphokine-activated killer (LAK) cells by recombinant interleukin-2 (IL-2) and the dependence of this phenomenon on DNA synthesis. Doses of gamma-irradiation (1000-5000 rads) that profoundly reduced DNA synthesis in human peripheral blood mononuclear leucocytes (PBL) also effectively suppressed the development of cytotoxic activity in the absence of IL-2. However, the same doses of irradiation affected the induction of LAK activity by IL-2 to a much lesser extent. Blocking the formation of deoxyribonucleotides by hydroxyurea, which resulted in a complete inhibition of DNA synthesis in PBL or purified T lymphocytes, had virtually no effect on the generation of LAK cells. These results indicate that the expression of LAK activity is not dependent on DNA synthesis.

Cytotoxicity, Immunologic↗
PubMed1987

The effect of bone marrow regulatory peptides on antibody production by hybridoma cells.

Peptides produced by bone marrow cells (myelopeptides) increase antibody production. Since antibody producing cells seemed to be their targets, we tested in these experiments the effect of myelopeptides on antibody production by 2B2 and 2C12 hybridoma cells. Both hybridomas produce anti-SRBC monoclonal antibodies of the IgM class. The 2B2 cells do not produce direct haemolytic plaques and less than 5% of them produce the indirect ones during the 90-min assay period. When they were cultivated with myelopeptides for 15 h, the number of indirect plaques increased two-fold. A slightly lower increase was observed after 24 h of incubation, while the 48-h incubation period did not increase the number of detected plaques. After 6 h of preincubation, only a slight increase in indirect plaque numbers was observed. About 25% of the 2C12 hybridoma cells produce both direct and indirect haemolytic plaques during the assay period. The effect of myelopeptides was studied only on the indirect ones and no clear effect was observed. Only after the 15-h incubation period a slight increase in plaque numbers was observed. Because the myelopeptides affect antibody production of hybridoma cells, antibody producing cells are evidently the targets of these substances. It remains to be established, whether they are the only target cells in the myelopeptide action on the immune response.

Animals↗
PubMed1985

The effect of thymectomy on immunological tolerance to human serum albumin in chickens.

The effect of thymectomy performed on the day of hatching has been studied in chickens rendered tolerant by 100 mg of HSA injected also on the day of hatching. After challenge at the age of 6 and 9 weeks, no significant difference was observed between the group of tolerant chickens, in which the thymectomy was complete or incomplete, and the non-operated tolerant one. The delayed recovery from tolerance observed in mammals was not seen even in chickens in which thymus was removed completely and no thymic residue remained. The anti-HSA antibodies were even slightly higher in thymectomized birds than in the non-operated ones but the difference was statistically non-significant.

Animals↗
PubMed1984

Antibody-producing cells in chickens tolerant to human serum albumin.

Cells forming antibodies to HSA were determined by the haemolytic plaque technique in the spleens of chickens in which tolerance to HSA was induced on the day of hatching. After immunization with HSA 2 weeks after hatching, no anti-HSA PFC or their very low numbers were observed in chickens rendered tolerant by the dose of 100 mg HSA. In a considerable proportion of the chickens, in which tolerance was induced by 1 mg or 0.1 mg of HSA, PFC were detected, though in statistically significantly lower numbers than in control birds. In tolerant chickens receiving 100 mg of HSA after hatching, the number of PFC after immunization at 4 weeks of age was statistically significantly and at 6 weeks non-significantly lower than in the controls. After immunization with BSA at 4 weeks of age, chickens injected with 100 mg HSA after hatching had the number of anti-HSA plaque-forming cells higher than the controls, but the difference was not statistically significant.

Animals↗
PubMed1984

Induction of tolerance in chickens by low doses of human serum albumin administered after hatching.

The possibility was tested whether tolerance can be induced in newly hatched chickens by a single injection of HSA on the day of hatching in doses one or several orders lower than the dose employed in previous experiments (100 mg of HSA). Doses of 10 and 1 mg of HSA induced a statistically significant suppression of anti-HSA antibody formation after challenge at the age of 2 and 4 weeks. Injection of 0.1 mg of HSA into newly hatched chickens also produced a statistically significant decrease in antibody formation after challenge at 2 weeks of age.

Animals↗
PubMed1982

Specific unresponsiveness to sheep red blood cells visualized by levamisole in athymic nude mice.

The administration of levamisole at the time of and 2 days after challenge with 10(8) SRBC significantly increased the direct anti-SRBC PFC response of nude mice. Pretreatment of nude mice of BALB/c and C 57 B1/10Sn strains with 10(9) or 10(8) SRBC injected 14 and 7 days before challenge suppressed the increase of the immune response. Pretreatment with 10(7) SRBC did not induce this inhibition. Administration of levamisole at the time of pretreatment with SRBC did not prevent the induction of inhibition. It is suggested that B cell exhaustion is the cause of the observed unresponsiveness.

Animals↗
PubMed1982

Inhibitory effects of 5-azapyrimidine nucleosides on cellular immunity.

The effect of 5-azacytidine (5-AzCR) and 5-aza-deoxycytidine (5-AzCdR) on the survival of skin grafts in mice and rats, the action of these drugs on regional GVH reaction, as well as the formation of haemopoietic colonies (CFU-5) in the spleen were studied. Both drugs prolonged the life span of skin grafts when administered 24 hr before transplantation, or on the 4th post-transplantation day. However, they were little effective when injected 24 hr after skin grafting, or after induction of the regional GVHR. Following intraperitoneal administration, they inhibited CFU-5 formation. Two-hour incubation in vitro of cells with 5-AzCR significantly reduced their GVH reactivity and capacity to form CFU-5; 5-AzCdR under the same conditions was ineffective.

Animals↗
PubMed1982

Immunological unresponsiveness to HSA in chickens.

HSA injected into chickens after hatching induces suppression of anti-HSA antibody formation. Unresponsive chickens react by producing the anti-HSA antibodies earlier and more intensively after BSA challenge than after challenge with HSA. This effect cannot be ascribed to T cells, because they were found to play no substantial role in the unresponsiveness to HSA. Neither was active suppression, which could account for the depressed antibody production, detected. B cell inactivation seems to be the major mechanism involved in this unresponsiveness. However, some additional mechanism must prevent B cells of unresponsive chickens from producing anti-HSA antibodies after HSA challenge, although they are able to form them after immunization with BSA. We suggest that cellular interactions, either between B cells of different specificities or between B cells and macrophages, are responsible for this differential reactivity.

Animals↗
PubMed1981

Antibody production stimulating activity of bone marrow cells from tolerant rats.

The antibody production stimulating activity of BM cells from SRBC-tolerant and normal rats were studied. Tolerance was induced by repeated injections of SRBC which were begun within 24 h after birth. BM cells obtained from tolerant animals 14-24 days after the last SRBC injection or from normal rats of the same age were used. LN cells from mice immunized with SRBC or BRBC served for the detection of BM activity. Four days after the second injection of antigen, LN cells were removed and cultivated alone or with BM cells from tolerant or control rats for 16 h. After cultivation, immune reaction was estimated by enumeration of indirect PFC. BM cells from SRBC-tolerant rats increased the number of SRBC PFC in the culture more than BM cells from control rats. On the other hand, the stimulatory activity of the BM cells from SRBC-tolerant animals for the BRBC-PFC was lower than that of normal BM cells or it was completely absent. The implications of these findings for the mechanism of the stimulating BM activity are discussed.

Animals↗
PubMed1980

Chromosomal aberrations in mouse bone marrow cells and antibody production changes induced by long-term exposure to cyclophosphamide and alpha-tocopherol.

The frequency of chromosomal aberrations in bone marrow cells and the primary immne response to sheep erythrocytes were studied at weekly intervals in mice exposed to cyclophosphamide (0.01% or 0.02% concentration in drinking water) and/or alpha-tocopherol(1000 mg/kg intraperitoneally, twice a week) throughout 4 weeks. Both 0.01% and 0.02% CY concentrations induced approximately the same levels of aberrant cells (7.5 and 9.2%, respectively). No significant rise in the frequency of aberrant cells was observed during the four-week course of experiment. The lower (0.01%) concentration of CY significantly increased IgM haemagglutinin titres, while IgG titres decreased rapidly after 3 weeks of exposure; 0.02% CY suppressed almost completely both IgM and IgG antibody levels already after one week of treatment. Simultaneous application of alpha-tocopherol significantly increased the frequency of aberrant cells in 0.01% Cy-treated mice but had no effect on 0.02% CY-treated group. No considerable changes in antibody titres were induced by alpha-tocopherol in both CY-treated and untreated animals.

Animals↗
PubMed1979

Xenogeneic bone marrow stimulating effect in vitro on antibody-producing cells.

It was described earlier that in the tissue cultures of immune mouse LN cells the number of antibody producing cells was increased 2-3-fold when syngeneic of allogeneic nonimmune BM cells were included in the cultures. In these experiments, parallel mixed cultures were set up of mouse immune LN cells with non-immune BM cells of either syngeneic or xenogeneic origin (rat, pig and chicken). Xenogeneic BM also increased the number of PFC in the mixed cultures. The intensity of the stimulation effected by xenogeneic BM of all three species tested was comparable to that induced by syngeneic BM. The number of PFC in all types of the mixed cultures was significantly higher (P less than 0.005) than in the LN cell cultures alone. The differences between the effect of syngeneic and xenogeneic BM and between the xenogeneic BM cells of different origin were not statistically significant (P less than 0.05).

Animals↗
PubMed1978

Persistence of immunological tolerance to HSA in chickens after cell transfer to immunosuppressed hosts.

The nature of immunological tolerance to HSA in chickens was analyzed by means of spleen cell transfers to 3-day-old, cyclophosphamide-treated, syngeneic recipients. The cell donors were 2-week-old tolerant or control chickens. The primary challenge with HSA was done 26 days after cell transfer. Spleen cells from both control and tolerant donors restored the immunoglobulin levels and the ability to produce antibodies to SRBC to normal. While cells from normal donors also reconstituted the ability to form antibodies to HSA, the recipients of cells from tolerant donors either did not form detectable amounts or formed only low titres of these antibodies. The ability of cells from normal donors to respond by anti-HSA antibody formation, when transferred together with cells from tolerant donors, was neither suppressed nor decreased. Thus, tolerance to HSA in chickens was not reversible and the existence of an active immune process, causing its duration, could not be demonstrated.

Animals↗
PubMed1978

Termination of tolerance to HSA in chickens.

A major part of chickens made tolerant to HSA at hatching formed anti-HSA antibodies when immunized with cross-reacting antigen, the BSA, at 4 weeks of age, although tolerant birds immunized with HSA produced no detectable antibody levels. Immunization with HSA + BSA did not prevent anti-HSA antibody formation in tolerant chickens, but it seems that the escape from tolerance is more rapid in birds immunized with BSA only than in those immunized with HSA + BSA and/or HSA only.

Animals↗